The role of ecology in sexual selection in the Heteroptera

Abstract

In this thesis I explore our current view of sexual selection, with a focus on the insect sub-order Heteroptera and the role of ecology. I first review sexual selection in the Heteroptera across two chapters, presenting the diverse range of sexually selected phenotypes found in these bugs. In doing so, I highlight the limitations of a "model systems" approach to sexual selection. Next, I explore male mate choice in the seed bug Lygaeus simulans, a species with high rates of mating failure, suggestive of cryptic mate choice. It is unclear why males do not exhibit pre-copulatory choice and to investigate this I manipulated morphological cues of female fecundity (body width and genitalia extension). Mate choice trials revealed that these cues do not influence female mating success. I next assess the impact of environmental change on L. simulans life history, fecundity, and fertility in a multi-factorial experiment that manipulated temperature, the opportunity for sexual selection and reproductive interference. The results highlight transgenerational fitness effects plus interactions amongst environmental stressors, reinforcing the importance of ecological complexity. I then present a meta-analyses investigating the occurrence of endurance rivalry, an underdiscussed mechanism of sexual selection. I explore how this mechanism adds to the discussion surrounding the alignment of natural and sexual selection. My penultimate chapter explores the traditional assignment of sexually selected phenotypes to male and female sex-roles, the history of this categorisation, and the positives and negatives of this approach. Throughout my thesis, I find a tension between the general and specific approaches to sexual selection, and evolutionary biology more generally. This is the theme of my General Discussion in which I consider the incorporation of evolution into conservation biology and our progression towards a predictive evolutionary theory. Ecology is presented as a potential solution a way to embrace explanations of diversity.